Effects of Annealing Temperature on Properties of Ti-Ga-Doped ZnO Films Deposited on Flexible Substrates

An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga-doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 degrees C, 400 degrees C, and 450 degrees C, respectively. The X-ray diffraction (XRD) analysis results show that all of the films have a strong (002) Ga doped ZnO (GZO) preferential orientation. As the annealing temperature is increased to 400 degrees C, the optical transmittance increases and the electrical resistivity decreases. However, as the temperature is further increased to 450 degrees C, the transmittance reduces and the resistivity increases due to a carbonization of the PI substrate. Finally, the crystallinity of the ZnO film improves with an increasing annealing temperature only up to 400 degrees C and is accompanied by a smaller crystallite size and a lower surface roughness.